1. Field of the Invention
The present invention relates to apparatus for drawing blood from patients, and, in particular, to a check valve to be mounted within a fitting designed to be inserted into a patient to allow multiple blood samples to be drawn from the patient.
2. Description of the Prior Art
In drawing multiple blood samples from a patient for use in a variety of diagnostic medical tests, it is conventionally the practice to insert one needle fitting into the patient which is used to sequentially fill a series of containers for a variety of these tests. Usually a fitting having a needle mounted on both ends thereof has one needle inserted into the patient. Then a series of evacuated fluid containers used for the various blood tests, or alternatively syringes with a puncturable end seal, are inserted onto the opposite needle so that blood may be drawn through the fitting. When this is done however, usually blood drips from the patient from the open end of this double ended fitting between the drawing blood for the various samples. Also, when a syringe is used, it occasionally happens that a technician or aide who is drawing blood through the fitting with a syringe may inadvertently press down on the syringe re-injecting blood back from the syringe into the patient. Since it is often the practice when conducting various blood tests to include a reagent in the vessel being filled directly from the patient, it is occasionally the case that when such re-injection is made, unwanted or undesirable reagents may be inadvertently injected into the patient. Some prior art fitting included one movable needle which punctured a membrane to allow fluid flow only when a receptacle was attached to the fitting, but no prior art check valve is known suitable for use in such blood drawing apparatus.